Over 100 types of human papillomaviruses (HPVs) infect mucosal and cutaneous epithelium, causing benign and malignant tumors. About 6.2 million new cases of HPV sexually transmitted infections (STIs) are reported every year; >20 million people in the US are currently infected, and HPV is considered as the most common known STI worldwide. Overall, data suggest that a single sexual act can promote infection, indicating that the viruses are quite effective transmissible agents in vivo. Recently, we have been able to produce high-titer HPV stocks in the laboratory. Our studies using infectious HPV virions in cell culture studies and our colleagues' work with animal PVs indicate the viruses in general are poor at causing infections in vitro. We therefore postulate that the current monolayer cell culture PV infection model systems fail to accurately recapitulate the infectious process in vivo. Indeed, the major deficiencies in the study of genital HPV-related infections have included the lack of high titer infectious viral stocks and the lack of appropriate tissue-based model systems with which to study early infections, pathogenesis, and interventions. Our CENTRAL HYPOTHESIS is that monolayer cell cultures fail to display essential aspects of epithelial tissue HPV infections and important features of HPV infection establishment can be determined from 3-dimensional (3-D) tissue-based models. We will use high titer HPV virion stocks to pursue this program's goals, which are to establish more physiologically relevant 3-D tissue models of HPV genital infections and to answer basic and essential questions about the initiation of productive HPV infections. To address our central hypothesis, we will pursue SPECIFIC AIMS that encompass three biologically integrated, and increasingly complex systems with regard to sexually transmitted PV infections. In Aim 1 we will define requirements for HPV infection of cells in differentiated epithelium in vitro. In Aim 2 we will use a rodent genital infection model to identify the cell types that are susceptible to HPV infection and to further determine how wounding potentiates infection in vivo. In Aim 3 we will evaluate genital PV infection establishment in the context of our non-human model of STI HPV infections wherein primate anatomy and immune response can be assessed. Hypotheses regarding specific aspects of genital PV binding and infection are posed so that whether supported or refuted, we will increase our understanding of the molecular mechanisms of HPV-target cell interactions and the biology of epithelial tissue infection, areas vastly understudied. We expect this work will directly impact future development of broadly cross-protective prophylactic and therapeutic strategies for preventing persistent HPV STIs